The S6 Data Release

Run Overview

For full information about the noise performance of the detectors in S6, see the
paper
Sensitivity Achieved by the LIGO and Virgo Gravitational Wave Detectors during LIGO's Sixth and Virgo's Second and Third Science Runs:
arXiv |
DCC

The noise spectrum is a strong function of time, due to commissioning breaks which (mostly)
improved the detector performance during S6. See for example Fig 1 of arxiv:1203.2674

Data Quality

GWOSC data quality categories, or flags, are defined by each data analysis group:
Compact Binary Coalescence (CBC), Burst,
Continuous Waves (CW), and
Stochastic
for their analyses. For each flag, GWOSC data files contain a corresponding 1 Hz channel that marks times
that pass the flag as a "1" (good data), and times that fail the flag as a "0" (bad data).
A full list of S6 data quality categories can be seen on the
S6 channel definitions page.
The details of each category
are described in the references linked below. However, as a rough guide:

DATA (Data Available): Failing this level indicates that GWOSC data is not available at this
time.

CAT1 (Category 1): Failing a category 1 data quality check
indicates a severe problem with the data. Times that fail CAT1 flags
should not be searched for astrophysical signals.

CAT2 (Category 2): Failing a category 2 data quality check
indicates there was a major
instrumental problem at the time of data collection

CAT3 (Category 3): Failing a category 3 flag indicates a moderate concern
or possible problem at the time of data collection. These
are typically linked to times of statistically identified problems.

In general, data quality levels are defined in a cumulative way: a time
which fails a given category automatically fails all higher
categories. For example, if the only known problem with a given time
fails a burst category 2 flag, then the data is said to pass DATA and
BURST_CAT1, but fails BURST_CAT2 and BURST_CAT3.

More information on data quality can be found in these locations:

Step 3 and
Step 4 of the introductory tutorial show how to apply data quality flags

Technical Details

Hardware Injections

The S6 data set contains simulated astrophysical signals, known as hardware injections, used for testing and calibration.
The simulations represent the types of signals sought by each of the four LIGO data analysis working groups.
Documentation on working with hardware injections
can be seen in the Find a Hardware Injection Tutorial.
Complete documentation of these "hardware injections" can be found by following the links below: